Sir Ian McKellen has worked with fellow "Sherlock Holmes" actors Benedict Cumberbatch and Sir Christopher Lee in "The Lord of the Rings" film series. He is also the second notable Marvel Films actor to take the role of Sherlock Holmes, after Robert Downey Jr..
The film originally was titled "A Slight Trick of the Mind", after the Mitch Cullin novel it was based on, but the filmmakers changed it to the simpler and more accessible "Mr Holmes."